Background Maintenance of muscle strength with age enables independent living for longer and may protect against chronic disease. Developmental and adult factors are associated with level of adult grip strength but evidence about their influence on its decline is sparse. We used longitudinal data to test whether birthweight, motor and cognitive development and patterns of pubertal growth were associated with trajectories of adult grip strength, and operated independently or on the same pathways as adult factors.
Methods The sample comprised 3058 men and women (6975 observations) in the MRC National Survey of Health and Development, a population-based British birth cohort study with up to three measures of grip strength from 53 to 69 years. Developmental factors included birthweight, maternal reports of motor milestone attainment, childhood cognitive test scores, and growth parameters of size, tempo and velocity. Covariates included lifetime social class, and adult height, BMI, verbal memory test scores, educational qualifications, health conditions and behaviours. We fitted multilevel models with the intercept and slope as random effects, included a linear age term, controlled for adult height and tested for age and sex interactions with each factor; then adjusted the developmental factors for each adult factor.
Results In men, heavier birthweight and childhood weight, beginning to walk ‘on time’, and later puberty, and in women, earlier age at first standing, were associated with stronger grip strength (but not its decline) independently of other developmental and adult factors. In women, there was an association between higher childhood cognition and stronger grip strength (but not its decline) which was attenuated by education. Men of higher childhood cognition showed a slower decline in grip strength (by 0.068 kg/year, 95% confidence interval (CI) 0,024, 0.11 per 1SD, p=0.003): this latter association was attenuated by adult verbal memory which became increasingly positively associated with grip strength at later ages (by 0.10 kg/year, 95% CI 0.061, 0.15 per 1SD, p<0.001). In contrast, the positive association between adult BMI and grip strength in men weakened (by −0.057 kg/year, 95% CI −0.11,–0.0056 per 1SD, p=0.03).
Conclusion Patterns of growth, motor development and lifetime cognition have persisting associations with grip strength between midlife and old age. Associations with cognition strengthened over this 16 year period suggesting that grip strength increasingly reflects neural ageing processes. Interventions that promote muscle development by targeting developmental factors, or maintain muscle strength by targeting adult risk factors should increase the chance of an independent old age.
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